The membrane molecular events involved in proton transport processes in the renal tubule will be investigated by using isolated luminal and contraluminal plasma membrane vesicles derived from the proximal convoluted tubule and the collecting duct. Proton transport will be assessed directly by measuring proton secretion from vesicles loaded with ATP and indirectly by measuring the intravesicular ATP hydrolysis in the same vesicles. In addition, the generated pH gradients will be estimated by the use of fluorescent pH indicators. Besides ATP dependent processes also the question of sodium dependence of proton transport, especially in the collecting duct, will be investigated. After drfining the basic principles of proton transport across the membranes the action of various inhibitors, such as amiloride and acetazolamide, will be tested. The data obtained from these experiments will provide information about the transport system and driving forces involved in proton transport in the proximal tubule and in the collecting duct. This information will be important for a better understanding of acid-base regulation and its disorders.